Traffic coordinator for arterial traffic system

Abstract

A traffic coordinator is disclosed which utilizes a master unit and a plurality of secondary units wherein the secondary units are positioned at artery cross streets for controlling the main artery traffic in a coordinated fashion. Both the master unit and secondary units contain microprocessors for calculating parameters utilized in the coordination system. The coordination system may be installed in already existing timer-controlled intersections and serves to provide a highly efficient real time control of artery green bands, offsets and splits to achieve optimum traffic flow.

What is claimed is: 
     
       1. A coordinator for use with a plurality of controllers for coordinating traffic at least along an artery, each controller associated with a side street intersection for controlling traffic signals at said intersection, said coordinator comprising: (a) means for storing a plurality of values corresponding to cycle lengths, said cycle length values associated with platoons of traffic moving along said artery, and   (b) means connected to said storing means for retrieving said cycle length values and for sequentially controlling each of said plurality of controllers in an individual manner to effect said retrieved cycle length values at each associated intersection as said platoons of vehicles move along associated intersections of said artery to thereby coordinate said controllers and traffic along said artery.   
     
     
       2. A coordinator as recited in claim 1 further comprising: means for receiving input signals, and   means cooperating with said storing means for calculating said plurality of cycle length values in response to said input signals, whereby said stored cycle length values correspond to said calculated cycle length values.   
     
     
       3. A coordinator as recited in claim 2 wherein said calculating means and said means for receiving input signals form a master unit which further comprises means for transmitting said calculated cycle length values, and said means for storing and retrieving said plurality of cycle length values form a plurality of secondary units, each secondary unit associated with one of said plurality of controllers and each secondary unit further comprises means for receiving said transmitted calculated cycle length values from said master unit.   
     
     
       4. A coordinator as recited in claim 3 wherein said input signals are generated in response to vehicles. 
     
     
       5. A coordinator as recited in claim 4 wherein said input signals are generated in real time, and said calculating means of said master unit comprises means for calculating said cycle length values in real time for each of said platoons of vehicles. 
     
     
       6. A coordinator as recited in claim 5 wherein said calculating means of said master unit is programmable. 
     
     
       7. A coordinator as recited in claim 6 wherein each of said secondary units comprise programmable calculating means. 
     
     
       8. A coordinator as recited in claim 7 wherein said input signals comprise volume signals generated from volume detectors positioned to sense vehicle volume entering said artery, said calculating means of said master unit calculating said cycle length values in response to said vehicle volume signals. 
     
     
       9. A coordinator as recited in claim 8 wherein said cycle length value consists of a red band time and a green band time and said programmable calculating means of said master unit calculates said cycle length value during a green band time and operates: (a) to monitor a gap time between successive volume signals,   (b) to compare the gap time to a reference time to determine when the gap time exceeds the reference time to establish a gapout condition,   (c) to count the number of volume signals corresponding to traffic actuations, A R , by vehicles during at least the artery red band time immediately preceding the artery green band time,   (d) to multiply the number A R  by a red headway time E R  to form a product T R ,   (e) to determine if a gapout condition occurs prior to a maximum green band time, and, (i) to determine the quantity T G  =(A G )(E G ) where, A g  is the number of actuations during the green band time prior to the occurrence of the gapout condition, and   E g  is a green headway time, and     (ii) to compare the quantity S G  =T R  +T G  to the time at which the gapout condition occurs from the start of the green band time, and   (iii) to select the larger of the two compared times as the calculated green band time to establish said cycle length for transmission to said secondary units, and     (f) to restrict the cycle length value transmitted to said secondary units to correspond to a green band time less than or equal to said maximum green band time.   
     
     
       10. A coordinator as recited in claim 9 wherein said reference time is a linear decreasing function time. 
     
     
       11. A coordinator as recited in claim 10 wherein said master unit comprises manually operable switches for selecting the slope of said linear decreasing function of time. 
     
     
       12. A coordinator as recited in claim 9 wherein said master unit further comprises manually operable switches for selecting said maximum green band time. 
     
     
       13. A coordinator as recited in claim 9 wherein said programmable calculating means of said master unit further operates to restrict the cycle length value transmitted to said secondary units to correspond to a green band time greater than or equal to a minimum green band time. 
     
     
       14. A coordinator as recited in claim 13 wherein said master unit further comprises manually operable switches for selecting said minimum green band time. 
     
     
       15. A coordinator as recited in claim 9 wherein said master unit further comprises manually operable switches for selecting said red headway time A R . 
     
     
       16. A coordinator as recited in claim 9 wherein said master unit further comprises manually operable switches for selecting said green headway time A G . 
     
     
       17. A coordinator as recited in claim 9 wherein said input signals further comprise occupancy signals, said occupancy signals generated from occupancy vehicle detectors positioned to sense vehicle occupancy within said artery. 
     
     
       18. A coordinator as recited in claim 17 wherein said occupancy signals have a variable pulse width corresponding to vehicle occupancy and said master unit further comprises means for converting said variable pulse width signals into a corresponding cycle length value. 
     
     
       19. A coordinator as recited in claim 18 wherein said converting means comprises means for selecting a linear function of cycle length values to pulse width signals. 
     
     
       20. A coordinator as recited in claim 19 wherein said selecting means comprises manually operable switches on said master unit. 
     
     
       21. A coordinator as recited in claim 20 wherein said manually operable switches select end points of said linear function to correspond to green band time values having said minimum green band time and said maximum green band time. 
     
     
       22. A coordinator as recited in claim 18 wherein said calculating means of said master unit further operates to select the larger of the cycle length values as calculated in response to said volume and occupancy input signals for transmission to said secondary units. 
     
     
       23. A coordinator as recited in claim 8 wherein said input signals further comprise occupancy signals, said occupancy signals generated from occupancy vehicle detectors positioned to sense vehicle occupancy within said artery. 
     
     
       24. A coordinator as recited in claim 23 wherein said occupancy signals have a variable pulse width corresponding to vehicle occupancy and said calculating means of said master unit further comprises means for converting said variable pulse width signals into a corresponding cycle length value. 
     
     
       25. A coordinator as recited in claim 24 wherein said converting means comprises means for selecting a linear function of cycle length values to pulse width signals. 
     
     
       26. A coordinator as recited in claim 24 wherein said calculating means of said master unit further comprises means for selecting the larger of the cycle length values as calculated in response to said volume and occupancy input signals for transmission to said secondary units. 
     
     
       27. A coordinator as recited in claim 25 wherein said selecting means comprises manually operable switches on said master unit. 
     
     
       28. A coordinator as recited in claim 27 wherein said calculated cycle length consists of a red band time and a green band time and said manually operable switches select end points of said linear function to correspond to green band values having a minimum green band time and a maximum green band time, said master unit further comprising means for setting said minimum and maximum green band times. 
     
     
       29. A coordinator as recited in claim 28 wherein said master unit further comprises manually operable switches for selecting said red band time. 
     
     
       30. A coordinator as recited in claim 28 wherein said master unit further comprises manually operable switches for selecting a plurality of red band times, said master unit comprising means for selecting said red band times in response to the value of said calculated green band time. 
     
     
       31. A coordinator as recited in claim 9 wherein each of said plurality of secondary units comprises means for selecting an offset value in time units, said offset value selectable independently of said calculated cycle length values. 
     
     
       32. A coordinator as recited in claim 31 wherein each of said plurality of secondary units comprises means for manually selecting said offset value, and wherein said secondary units are positioned adjacent said associated controllers. 
     
     
       33. A coordinator as recited in claim 9 wherein said coordinator is operable in an inbound and outbound mode, said inbound mode operative for coordinating said plurality of controllers to produce a favored inbound direction of traffic flow and said outbound mode operative for coordinating said plurality of controllers to produce a favored outbound direction of traffic flow. 
     
     
       34. A coordinator as recited in claim 33 wherein said master unit further comprises means for selecting separate values for E R  and E G  corresponding to each of said inbound and outbound modes and said calculating means of said master unit operates to utilize same in calculating the quantity S G  for the corresponding modes. 
     
     
       35. A coordinator as recited in claim 34 wherein said means for selecting said separate values for E R  and E G  of said master unit comprises manually operable switches. 
     
     
       36. A coordinator as recited in claim 8 wherein each of said plurality of secondary units comprises means for selecting an offset value in time units, said offset value selectable independently of said calculated cycle length values. 
     
     
       37. A coordinator as recited in claim 36 wherein said time units is seconds of vehicle travel time. 
     
     
       38. A coordinator as recited in claim 37 wherein each of said plurality of secondary units comprises means for manually setting said offset value. 
     
     
       39. A coordinator as recited in claim 38 wherein said secondary units are positioned adjacent said associated controllers. 
     
     
       40. A coordinator as recited in claim 36 wherein said input signals further comprise occupancy signals generated from occupancy vehicle detectors positioned to sense vehicle occupancy within said artery. 
     
     
       41. A coordinator as recited in claim 40 wherein said master unit further comprises means for changing the offset value of said secondary units in response to said occupancy signals. 
     
     
       42. A coordinator as recited in claim 41 wherein said master unit comprises manually operable switches for enabling selection of the change in offset value. 
     
     
       43. A coordinator as recited in claim 42 wherein said master unit further comprises manually operable switches associated with said switches for enabling selection of the change in offset value, said associated switches corresponding to setpoint occupancy values, whereby different changes in offset values are selected in response to different values of occupancy. 
     
     
       44. A coordinator as recited in claim 3 wherein each of said plurality of secondary units comprises means for selecting an offset value in time units, said offset value selectable independently of said calculated cycle length values. 
     
     
       45. A coordinator as recited in claim 44 wherein said time units is seconds of vehicle travel time. 
     
     
       46. A coordinator as recited in claim 45 wherein each of said plurality of secondary units comprises means for manually selecting said offset value. 
     
     
       47. A coordinator as recited in claim 46 wherein said secondary units are positioned adjacent said associated controllers. 
     
     
       48. A coordinator as recited in claim 9 wherein said calculating means of said master unit additionally operates to count the number of actuations during a last car passage time (LCP) immediately preceding said red band time, and said quantity T R  is formed by:   T.sub.R =(A.sub.R +LCP)E.sub.R     
     
     
       49. A coordinator as recited in claim 48 wherein said coordinator is operable in an inbound and outbound mode, said inbound mode operative for coordinating said plurality of controllers to produce a favored inbound direction of traffic flow and said outbound mode operative for coordinating said plurality of controllers to produce a favored outbound direction of traffic flow. 
     
     
       50. A coordinator as recited in claim 49 wherein said master unit further comprises means for selecting separate values for LCP corresponding to each of said inbound and outbound modes. 
     
     
       51. A coordinator as recited in claim 3 wherein said coordinator is operable in an inbound and outbound mode, said inbound mode operative for coordinating said plurality of controllers to produce a favored inbound direction of traffic flow and said outbound mode operative for coordinating said plurality of controllers to produce a favored outbound direction of traffic flow. 
     
     
       52. A coordinator as recited in claim 51 wherein said input signals comprise volume and occupancy signals and said calculating means of said master unit calculates a cycle length value in response to said volume and occupancy signals and further comprises means for selecting the larger of said calculated cycle length values for transmission of same to said secondary units. 
     
     
       53. A coordinator as recited in claim 52 wherein said coordinator is operative in an average mode and said master unit further comprises means for generating average cycle length values. 
     
     
       54. A coordinator as recited in claim 53 wherein said master unit comprises a plurality of manually operable switches for setting a plurality of average cycle length values and means for selecting one of said values for transmission to said secondary units in said average mode. 
     
     
       55. A coordinator as recited in claim 54 wherein said selecting means comprises means for averaging said larger value of cycle length in said inbound mode with said larger value of cycle length in said outbound mode and means for comparing said average value with said set plurality of cycle length values. 
     
     
       56. A coordinator as recited in claim 3 wherein said secondary units comprise means for retrieving said last received cycle length value for controlling said controllers in the event of communication breakdown between said master and secondary units. 
     
     
       57. A coordinator as recited in claim 3 wherein said secondary units comprise means for sending force-off commands to said associated controllers for controlling same. 
     
     
       58. A coordinator as recited in claim 57 wherein said secondary units comprise manually operable switches for selecting times for issuing said force-off commands for different phases of traffic flow. 
     
     
       59. A coordinator as recited in claim 58 wherein said selected times are in seconds. 
     
     
       60. A coordinator as recited in claim 59 wherein said force-off commands are selectable independently of cycle length values. 
     
     
       61. A coordinator as recited in claim 2 further comprising means for sending force-off commands to said associated controllers for controlling same. 
     
     
       62. A coordinator as recited in claim 61 further comprising manually operable switches for selecting times for issuing said force-off commands for different phases of traffic flow. 
     
     
       63. A coordinator as recited in claim 62 wherein said force-off commands are selectable independently of cycle length values. 
     
     
       64. A coordinator as recited in claim 2 wherein said coordinator is operable in an inbound and outbound mode, said inbound mode operative for coordinating said plurality of controllers to produce a favored inbound direction of traffic flow and said outbound mode operative for coordinating said plurality of controllers to produce a favored outbound direction of traffic flow. 
     
     
       65. A coordinator as recited in claim 64 wherein said input signals comprise volume and occupancy signals and said calculating means calculates a cycle length value in response to said volume and occupancy signals and further comprises means for selecting the larger of said calculated cycle length values for controlling said plurality of controllers. 
     
     
       66. A coordinator as recited in claim 65 wherein said coordinator is operative in an average mode and comprises means for generating average cycle length values. 
     
     
       67. A coordinator as recited in claim 66 further comprising a plurality of manually operable switches for setting a plurality of average cycle length values and means for selecting one of said average cycle length values for controlling said plurality of controllers in said average mode. 
     
     
       68. A coordinator as recited in claim 67 wherein said means for selecting one of said average cycle length values comprises means for averaging said larger value of calculated cycle length from an inbound mode with said larger value of calculated cycle length from an outbound mode. 
     
     
       69. A coordinator as recited in claim 1 wherein said coordinator is operable in an inbound and outbound mode, said inbound mode operative for coordinating said plurality of controllers to produce a favored inbound direction of traffic flow and said outbound mode operative for coordinating said plurality of controllers to produce a favored outbound direction of traffic flow. 
     
     
       70. A coordinator as recited in claim 69 wherein said coordinator is operative in an average mode and comprises means for generating average cycle length values, said coordinator further comprising: means for sensing vehicles entering said artery in both inbound and outbound directions to provide inbound and outbound direction signals, and   means for selecting an inbound, outbound or average mode in response to said inbound and outbound direction signals.   
     
     
       71. A coordinator as recited in claim 1 further comprising means for selecting offset values for said controllers in time units, said offset values selectable independently of said cycle length values. 
     
     
       72. A coordinator as recited in claim 71 wherein said time units are in seconds of vehicle travel time. 
     
     
       73. A traffic coordination system controlling vehicle traffic flow along a main traffic artery and a plurality of side street intersections comprising: (a) a master unit having programmable computing means,   (b) at least one inbound and one outbound volume vehicle detector each measuring vehicles entering said artery and for providing inbound and outbound vehicle volume signals to said master unit in response to inbound and outbound vehicle volume respectively, said inbound and outbound vehicle detectors positioned proximate opposite extremities of the artery under control by said coordination system,   (c) at least one inbound and one outbound occupancy vehicle detector for providing inbound and outbound occupancy signals to said master unit in response to inbound and outbound vehicle occupancy respectively, said inbound and outbound occupancy detectors positioned within said artery and removed from said corresponding inbound and outbound volume detectors,   (d) a plurality of secondary units each unit interconnected to said master unit and having means for receiving and storing data therefrom,   (e) said master unit computing means comprising means for calculating a cycle length value for artery traffic in response to received vehicle volume and occupancy signals,   (f) a plurality of controllers, one controller connected for operating traffic signals at each side street intersection of said artery, and   (g) a secondary unit connected to each controller for providing traffic signal control commands thereto in response, at least in part, to data received and stored from said master unit,   whereby traffic is coordinated along said artery in response to sensed vehicle flow.   
     
     
       74. A traffic coordination system as recited in claim 73 wherein each secondary unit issues force-off commands to associated controllers for terminating a green time interval in response to data from said master unit. 
     
     
       75. A traffic coordination system as recited in claim 73 wherein said system is operable in inbound, outbound and average modes of operation as determined by said master unit in response to said vehicle volume signals, said inbound mode effective to favor inbound traffic flow, said outbound mode effective to favor outbound traffic flow and said average mode effective to favor average traffic flow. 
     
     
       76. A traffic coordination system as recited in claim 75 wherein said computing means of said master unit calculates a cycle length value appropriate for a platoon of vehicles sensed in real-time and transmits data corresponding to said calculated cycle length value to each of said secondary units. 
     
     
       77. A traffic coordination system as recited in claim 76 wherein said means for storing data of each secondary unit comprises memory storage means for storing cycle length values received from said master unit and each secondary unit further comprises means for retrieving said cycle length values for providing said traffic signal control commands to said connected controller after a period of time determined by an offset value, whereby each platoon of vehicles may be optimally passed through each intersection by application of the associated stored cycle length value upon arrival of said platoon at each intersection. 
     
     
       78. A traffic coordination system as recited in claim 76 wherein said means for receiving and storing said cycle length values comprises programmable computing means. 
     
     
       79. A traffic coordination system as recited in claim 78 wherein each secondary unit comprises means for selecting said offset value in time units, said offset value selectable independently of said cycle length values. 
     
     
       80. A traffic coordination system as recited in claim 79 wherein said offset value is selectable in seconds. 
     
     
       81. A traffic coordination system as recited in claim 78 wherein said secondary unit comprises means for presetting said offset value in percent of cycle length value. 
     
     
       82. A traffic coordination system as recited in claim 78 wherein each secondary unit is positioned adjacent said connected controller at the corresponding side street intersection. 
     
     
       83. A traffic coordination system as recited in claim 73 wherein each secondary unit is positioned adjacent said connected controller. 
     
     
       84. A traffic coordination system as recited in claim 83 wherein each secondary unit comprises means for selecting the offset value independently of said cycle length values. 
     
     
       85. A method of coordinating a plurality of traffic signal lights associated with side street intersections for controlling traffic at said intersections and along a common roadway comprising steps of: (a) storing a plurality of cycle length values, said cycle length values associated with groups of vehicles moving along said roadway,   (b) automatically retrieving said stored cycle length values, and   (c) automatically, sequentially and individually controlling said traffic signal lights in response to said retrieved cycle length values at offset times corresponding to the position along said roadway of the side street intersections, thereby producing cycle lengths at said intersections corresponding to said retrieved cycle length values.   
     
     
       86. A method as recited in claim 85 further comprising the steps of: (a) receiving input signals, and   (b) automatically calculating from said received input signals said cycle lengths values.   
     
     
       87. A method as recited in claim 86 further comprising the steps of sensing vehicles entering said roadway and generating said input signals in response to said sensed vehicles to provide a directional coordination of said traffic signal lights for said groups of vehicles entering said coordinated roadway. 
     
     
       88. A method as recited in claim 87 wherein said sensing step comprises sensing vehicles entering said roadway in both an inbound and outbound direction and generating input signals in response thereto to provide a directional coordination of said traffic light signals in response to sensed inbound vehicles and sensed outbound vehicles. 
     
     
       89. A method as recited in claim 88 further comprising the steps of: (a) sensing vehicles within said coordinated roadway,   (b) generating additional input signals in response to said vehicles sensed within said coordinated roadway, and   (c) calculating said cycle length values from said input signals and said additional input signals.   
     
     
       90. A method as recited in claim 89 further comprising the steps of: (a) calculating a modification of said offset times in response to said additional input signals, and   (b) controlling said traffic light signals at said modified offset times.   
     
     
       91. A method as recited in claim 88 further comprising the steps of: (a) sensing vehicles within said coordinated roadway,   (b) generating additional input signals in response to said vehicles sensed within said coordinated roadway,   (c) calculating a modification of said offset times in response to said additional input signals, and   (d) controlling said traffic light signals in response at said modified offset times.   
     
     
       92. A method as recited in claim 89 wherein said calculating step comprises: calculating one cycle length value in response to said input signals,   calculating another cycle length value in response to said additional input signals, and   said method further comprising the steps of selecting the larger cycle length value from said one and another cycle length values and storing said selected larger value for coordinating said traffic signal lights.   
     
     
       93. A method as recited in claim 92 wherein the step of sensing the vehicles entering said roadway comprises sensing vehicle volume and the step of sensing vehicles within said roadway comprises sensing vehicle occupancy. 
     
     
       94. A method as recited in claim 93 wherein the step of sensing the vehicles entering said roadway comprises sensing vehicle volume and the step of sensing vehicles within said roadway comprises sensing vehicle occupancy. 
     
     
       95. A method as recited in claim 85 further comprising the step of sensing vehicles on said roadway to provide inbound, outbound and average modes of coordinating said traffic signal lights. 
     
     
       96. A method as recited in claim 85 wherein the step of controlling said traffic signal lights comprises the step of generating force-off command signals to controllers associated with said traffic signal lights. 
     
     
       97. A method as recited in claim 85 further comprising the steps of: (a) sensing vehicle volume entering said coordinated roadway for providing input vehicle volume signals, and   (b) calculating the cycle length value in real time from said input vehicle volume signals for the group of vehicles being sensed,   whereby said stored cycle length values correspond to groups of sensed vehicles entering said coordinated roadway.   
     
     
       98. A method as recited in claim 97 wherein said cycle length values comprise red band times and green band times and said calculating step comprises calculating a gap time between successive sensed vehicles and terminating said green band time in response, at least in part, to said gap time. 
     
     
       99. A method as recited in claim 98 wherein the step of controlling said traffic signal lights comprises the step of generating force-off command signals to controllers associated with said traffic signal lights. 
     
     
       100. A method as recited in claim 99 wherein said step of terminating said green band time further comprises calculating the number of input vehicle volume signals and delaying the termination of said green band time for numbers exceeding a reference value. 
     
     
       101. A method of coordinating a plurality of traffic signal lights positioned along a common roadway for controlling said roadway and a plurality of side street intersections comprising the steps of: (a) sensing vehicles along said roadway to provide input signals to a master unit,   (b) calculating in said master unit cycle length values in real time corresponding to said sensed vehicles,   (c) transmitting said cycle length values to a plurality of secondary units, each secondary unit associated with a side street intersection,   (d) storing said cycle length values in said secondary units,   (e) individually retrieving said cycle length values in said secondary units for sequential application as force-off commands to associated controllers controlling said traffic signal lights at said side street intersections, and   (f) generating said force-off commands at said secondary units at offset times corresponding to the position of the secondary units along said roadway.   
     
     
       102. A method as recited in claim 101 wherein said sensing step comprises sensing vehicle volume entering said roadway for providing said input signals. 
     
     
       103. A method as recited in claim 102 wherein said sensing step further comprises sensing vehicle occupancy within said roadway for providing additional input signals, and said calculating step comprises calculating said cycle length values in response to said input signals and said additional input signals. 
     
     
       104. A method as recited in claim 101 wherein said sensing step comprises sensing vehicles entering said coordinated roadway in both inbound and outbound directions and said method further comprises the step of coordinating said traffic signal lights for favoring traffic flow in one of said inbound and outbound directions in response to the number of sensed inbound and outbound vehicles. 
     
     
       105. Apparatus for coordinating a plurality of traffic signal lights along an artery having a plurality of side street intersections comprising: (a) means for storing in sequence a plurality of cycle length values, said cycle length values associated with platoons of traffic moving along said artery, and   (b) means connected to said storing means for retrieving said cycle length values in sequence and for individually and sequentially controlling said plurality of traffic signal lights to effect said retrieved cycle length values at each associated intersection as said platoons of vehicles move along associated intersections of said artery to thereby coordinate said traffic along said artery.   
     
     
       106. Apparatus as recited in claim 105 further comprising: means for receiving input signals, and   means cooperating with said storing means for calculating said plurality of cycle length values in response to said input signals, whereby said stored cycle length values correspond to said calculated cycle length values.   
     
     
       107. Apparatus as recited in claim 106 wherein: said calculating means and said means for receiving input signals form a master unit which further comprises means for transmitting said calculated cycle length values, and   said means for storing and retrieving said plurality of cycle length values form a plurality of secondary units, each secondary unit associated with one of said plurality of side street intersections and further comprises means for receiving said transmitted calculated cycle length values from said master unit.   
     
     
       108. A coordinator as recited in claim 107 wherein said input signals are generated in response to vehicles. 
     
     
       109. A coordinator as recited in claim 108 wherein said input signals are generated in real time, and said calculating means of said master unit comprises means for calculating said cycle length values in real time for each of said platoons of vehicles. 
     
     
       110. Apparatus as recited in claim 109 wherein said input signals comprise volume signals generated from volume detectors positioned to sense vehicle volume entering said artery, said calculating means of said master unit calculating said cycle length values in response to said vehicle volume signals. 
     
     
       111. Apparatus as recited in claim 110 wherein said cycle length value consists of a green band time and a red band time and said transmitting means of said master unit comprises means for transmitting a sync signal during said green band time at a time related to the calculated cycle length value, and each of said plurality of secondary units comprises means for determining from said sync signal the calculated cycle length value. 
     
     
       112. Apparatus as recited in claim 111 wherein said sync signal corresponds to a change in state of a binary signal. 
     
     
       113. Apparatus as recited in claim 112 wherein said sync signal precedes the end of said green band time by a fixed time interval. 
     
     
       114. Apparatus as recited in claim 113 wherein said transmitting means of said master unit further comprises means for transmitting a coded message corresponding to said cycle length value, and each of said secondary units comprises means for decoding said coded message, whereby said coded message serves as a redundancy check of said received calculated cycle length values as determined from said received sync signal. 
     
     
       115. Apparatus as recited in claim 114 wherein said coded message is transmitted after said sync signal and during the red band time of the next cycle. 
     
     
       116. Apparatus as recited in claim 109 wherein each of said secondary units comprises first counter means for providing a unique running time count of each platoon within said coordinated artery, said running time count stored in said storing means with corresponding cycle length values of said platoons and means for retrieving said running time count and said corresponding cycle length values, whereby said running time count provides an offset value check for platoons passing through said intersections. 
     
     
       117. Apparatus as recited in claim 116 wherein each of said plurality of secondary units comprises a second counter means resettable at the end of each cycle length value for clocking operations within said secondary unit, said second counter means in synchronization with said platoons of vehicles passing through said corresponding intersections. 
     
     
       118. Apparatus as recited in claim 117 wherein each of said plurality of secondary units comprises a third counter means in synchronization with platoons of vehicles associated with said master unit and resettable at the end of cycle length values at said master unit, said first, second and third counter means operable to ensure coordinated vehicle flow through said artery. 
     
     
       119. A traffic coordinator for use on a roadway having a plurality of intersections and traffic lights and means for sensing vehicle traffic along said roadway, said sensing means including means for generating signals indicative of said sensed traffic, said coordinator comprising: (a) a master unit comprising: (i) input interface means for receiving said signals,   (ii) data processing means connected to said input interface means, said data processing means including a microprocessor, data memory storage means and program memory storage means for programming said microprocessor, said data processing means operable for calculating a cycle length value in response to said received signals and for generating cycle length signals corresponding thereto,   (iii) output interface means connected to said data processing means for transmitting said cycle length signals,     (b) a plurality of secondary units, one secondary unit associated with each of said intersections along said roadway and associated with an offset time from a preselected reference, each secondary unit comprising: (i) input interface means operable for receiving said transmitted cycle length signals from said master unit,   (ii) data processing means connected to said input interface means of said secondary unit and including a microprocessor, data memory storage means and program memory storage means for programming said microprocessor, said data processing means of said secondary unit operable for storing representations of said cycle length signals and for retrieving same in the order of storage for generating force-off command signals corresponding to said cycle length signals at time determined by said associated offset times, and   (iii) output interface means connected to said data processing means of said secondary unit for receiving said force-off command signals and for applying same to actuate traffic lights at said associated intersections.